well unfortunately the terms "light weight" and "low recoil" generally don't go together. All things being equal the heavier the gun the less the recoil. I generally think that starting a kid with a light weight single shot is a bad idea because it will kick like a mule and make shooting not fun. My first gun was a youth 870 20 gauge and I think that would be a pretty good starting point. It has a little more heft than a single shot (generally) but he should still be able to handle it, and it gives you the option of being a single shot (only give him one shell at a time) or a repeater. I'm quite sure they make a youth Remington 1100 as well. It will cost you quite a bit more i'm sure and it will likely be a little heavier but the gas system will soak up some of the recoil. If I was in your shoes (and i'm not so feel free to disregard any of this) I would probably go with the 870. If he tries it and it is either too heavy or kicks too hard I would put it in the gun safe and leave it there until next year because he is probably too little right now. I think it is better to wait an extra year and make sure he is physically ready, than to start him too soon and have him not enjoy himself because the gun tires him out and beats him up.